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This paper presents the results of field tests performed to investigate the compressive bearing capacity of pre-bored grouted planted (PGP) pile with enlarged grout base focusing on its base bearing capacity. The bi-directional O-cell load test was conducted to evaluate the behavior of full scale PGP piles. The test results show that the pile head displacements needed to fully mobilize the shaft resistance were 5.9% and 6.4% D (D is pile diameter), respectively, of two test piles, owing to the large elastic shortening of pile shaft. Furthermore, the results demonstrated that the PHC nodular pile base and grout body at the enlarged base could act as a unit in the loading process, and the enlarged grout base could effectively promote the base bearing capacity of PGP pile through increasing the base area. The normalized base resistances (unit base resistance/average cone base resistance) of two test piles were 0.17 and 0.19, respectively, when the base displacement reached 5% Db (Db is pile base diameter). The permeation of grout into the silty sand layer under pile base increased the elastic modulus of silty sand, which could help to decrease pile head displacement under working load. [ABSTRACT FROM AUTHOR]

The pre-bored grouted planted pile is a new type of composite pile foundation that consists of a precast concrete pile and the surrounding cemented soil. A series of shear tests were conducted in a specific shear test apparatus to investigate the shaft capacity of the different pile-soil interfaces. The test results show that the frictional capacity of the cemented soil-sand interface is controlled mainly by the sand properties, while the strength of the cemented soil slightly influences the interface properties by affecting the normalized roughness coefficient Rn. The frictional capacity of the concrete-sand interface is similar to the frictional capacity of the cemented soil-sand interface, and the existence of mud cake layer virtually hampers the frictional properties of the interface. The maximum skin friction of the concrete-cemented soil interface increases approximately linearly with the increasing cemented soil strength, and the value of the maximum skin friction is much larger than that of the cemented soil-sand interface of identical cemented soil strength, which demonstrates the integrity of the pre-bored grouted planted pile in the load transfer process. [ABSTRACT FROM AUTHOR]

A group of field tests and three-dimensional finite element simulation were used to investigate the behavior of the pre-bored grouting planted pile under compression and tension; moreover, a group of shear tests of the concrete-cemented soil interface was carried out to study the frictional capacity of the pile-cemented soil interface. The load-displacement response, shaft resistance and mobilized base load were discussed based on the measured and computed results. The measured and computed results show that the frictional capacity of the cemented soil-soil interface is better than the frictional capacity of the concrete-soil interface. The frictional capacity of the concrete-cemented soil interface is mainly controlled by the properties of the cemented soil, and the ultimate skin friction of the concrete-cemented soil interface is much larger than that of the cemented soil-soil interface. The frictional capacity of the soil layer close to the enlarged base is also promoted because of the compaction of the enlarged base. The enlarged cemented soil base can promote the behavior of the pile foundation under tension, and the enlarged cemented soil base undertakes approximately 26.3% of the total uplift load under the ultimate bearing capacity in this research. [ABSTRACT FROM AUTHOR]